Although the preparation of monomeric unsaturated mono- and difunctional compounds, such as mono- and dicarboxylic acid esters by an addition reaction of an olefin with a mono- or dicarboxylic acid ester is well known, as is taught in U.S. Pat. No. 3,783,136, the preparation of linear alpha, omega difunctional polymers by an olefin metathesis reaction typically has been limited to a few special cases where the reaction is specific for a certain few reactants.
The disproportionation or metathesis of olefins is a reaction in which one or more olefinic compounds are transformed into other olefinic compounds of different molecular weights. The disproportionation of an olefin to produce an olefin of higher molecular weight and an olefin of lower molecular weight can be a self-disproportionation reaction as propylene to ethylene and butene, or cross-disproportionation of two different olefins to produce still other olefins, also termed cross-metathesis of olefins.
The utility of the olefin disproportionation reaction, commonly termed an olefin metathesis reaction, has been recognized as a means to obtain olefinic compounds bearing functional reactive groups such as esters, ethers, halogens and others. However, inasmuch as the olefin metathesis reaction is an equilibrium reaction of unsaturated compounds, the usual consequences of an equilibrium reaction can be present, i.e., yields of the desired product can be low unless a suitable means of driving the reaction to completion can be utilized. Also, the catalyst present for the olefin metathesis reaction can initiate by-product reactions. The reverse of the olefin metathesis reaction can occur wherein the reaction products self-metathesize to form other olefinic compounds. Terminal olefins nave been found to self-metathesize rapidly such as in the industrial process for conversion of propylene to other products. The cis-trans configuration of the final product may be predominantly trans, or predominantly cis, or a mixture of cis-trans, depending upon reaction conditions, including the catalyst utilized.
The disproportionation of olefins bearing functional groups is an especially economically useful reaction in that compounds bearing functional groups are valuable for use in polymer formation and chemical transformations to yield industrially valuable products. Examples of functional reactive groups previously available are esters, alcohols, amines, halides. Monofunctional and difunctional hydrocarbon polymers of olefinic compounds having at least one internal carbon-to-carbon double bond wherein the functional groups are acrylates or methacrylates have not been previously available by disproportionation of olefins.
Polymers having terminal functional endgroups can be further reacted to form telechelic difunctional polymers. Telechelic polymers having functional groups useful for further reactions, i.e., cross-linking reactions or the construction of other defined polymer structures such as block copolymers, etc., are of great interest from the viewpoint of possible applications. A halogen-terminated polymer can be reacted with a unilaterally metal-terminated chain of another polymer to produce block copolymers. Hydroxy-terminated polymer chains can be reacted with di-and/or tri- polyisocyanates and/or analogous polyfunctional compounds such as acid chlorides of polybasic acids. Ester-terminated polymer chains can be reacted with alcohols or other reactive functional groups for adhesive, coating, fiber, foam and other applications.
Monofunctional and telechelic difunctional polymers have been prepared in the past by termination of living polymers with anionic, cationic and metathesis polymerizations of cyclic olefins. Metathesis polymerizations of cyclic olefins can restrict the availability of products to those which can be prepared from a relatively few cyclic olefins, typically of from about 5 to about 9 carbon atoms. Functional groups in monofunctional and difunctional polymers derived from cyclic olefins can be limited to those present in the precursor cyclic olefinic compounds. With acyclic olefins, the olefin metathesis reaction can result in cleavage and reforming of carbon-to-carbon double bonds. The resulting redistribution of alkylidene moieties leads to a random product distribution at equilibrium (Kirk-Othmer, Ency. Chem. Tech., 3rd ed., 8 (597). Telechelic difunctional hydrocarbon polymers produced via anionic or free-radical polymerizations of acyclic olefins typically are mixtures of polymer structures. For example, alpha-omega difunctional polybutadienes prepared by anionic or free-radical polymerization of butadiene contain mixtures of 1,4- and 1,2- polybutadiene structures, have molecular weights of 1000-4000 and are terminated with hydroxy or carboxy functionalities. Typically, the functionalities are less than difunctional, the functionality number (Fn) being less than 2; or greater than difunctional, the functionality number being greater than 2,and the products are mixtures of mono-functional, difunctional, trifunctional, and non-functional species.
This invention accordingly relates to a process for preparation of non-crosslinked linear telechelic oligomers and polymers of high difunctional purity by olefin metathesis reaction. The product of the reaction can be further reacted to prepare difunctional alcohols, acids and amines.
The linear acyclic functional olefinic compound product is prepared by reacting a monofunctional acyclic olefinic compound selected from the group consisting of alkyl acrylates and alkyl methacrylates with a second olefin in a cross metathesis reaction wherein the second olefin is selected from the group consisting of a cyclic olefinic non-conjugated compound of from 4 to 30 carbon atoms and an acyclic unsaturated hydrocarbon polymer of number average molecular weight of up to about 1,000,000. The product of the reaction between the monofunctional olefinic compound and a second olefinic compound can be a mixture of species; i.e., monofunctional, difunctional and nonfunctional. Conversion of reactants is at least 10% of theoretical based on olefinic compound reactants.
The invented process utilizes a catalyst composition comprising (a) a transition metal chloride, oxyhalide, oxide or ammonium salt, (b) an organic tin compound or aluminum halide reagent, and (c) an organic Lewis base, wherein undesired side reactions such as double bond migration are minimized.
The non-reactivity of certain unsaturated compounds such as alkyl acrylates and alkyl methacrylates in the olefin metathesis reaction, i.e., methyl methacrylate, has been documented, K. J. Ivin, Olefin Metathesis, Academic Press, London, N.Y., (1983), 151. Dialkyl maleates or fumarates have been reported to be virtually unreactive in olefin metathesis reactions, Verkuijlen, et al. Recl. Trav. Chim., Pays-Bas (1977), 96, M86. However, dimethyl-3-hexene-1,6-dioate, which is costly and is not commercially available in bulk quantities, has been reported to cross-metathesize with 1,5-cyclooctadiene, Reyx, et al. Makromol. Chem. (1982), 183, 173-183, cyclopentene, Reyx, et al., J. Molecular Catal., (1986), 36, 101-105, or norbornene, and has been shown to yield oligomers/polymers which are not high in difunctional purity, Cramall, et al., J. Molecular Catal., (1991), 65, 193-203.
Surprisingly, it has been found that linear functional acyclic olefinic compounds comprising monofunctional unsaturated polymers containing groups such as acrylates and methacrylates can be prepared in the presence of the catalyst composition of the instant invented process in cross-metathesis reactions of alkyl acrylates or alkyl methacrylates with acyclic or cyclic olefinic non-conjugated compounds.
In the process of the instant invention, in the presence of reactants comprising cyclic olefinic non-conjugated compounds and polymeric olefinic compounds with functional olefinic compounds such as acrylates or methacrylates, linear difunctional telechelic unsaturated polymers are prepared with at least one internal carbon-to-carbon double bond and ester groups such as acrylate or methacrylate terminal groups. These linear non-crosslinked difunctional telechelic unsaturated polymers with reactive terminal groups are suitable for further functionalization or incorporation into other polymers for preparation of block copolymers and other products.
The linear nonocrosslinked difunctional telechelic unsaturated polymers prepared by the process of this invention are true linear compounds of strictly regular structure with exactly defined terminal groups. Such polymers with acrylate or methacrylate endgroups have not heretofore been produced.
Although acyclic unsaturated compounds containing functional groups have been prepared by the olefin metathesis reaction, it has been indicated that when the functional group is too close to the double bond, the metathesis reaction does not work. The non-reactivity of methyl methacrylate has been ascribed to this, K. J. Ivin Olefin Metathesis, Academic Press, London, N.Y., (1983), 149-151. It has been found that in the process of the instant invention, olefinic compounds such as methyl methacrylate can be reacted to prepare monofunctional and telechelic difunctional oligomers or polymers by olefin metathesis reactions.
As is well known, side reactions can occur during olefin metathesis reactions. These side reactions include alkylation, isomerization, cyclization and addition across double bonds present in the molecular structure. Surprisingly, it has been found that in cross-metathesis reactions under the conditions of the present invention, these side reactions are minimal. The average functionality number of monofunctional polymers prepared by the process of this invention is at least 0.7 as determined by nuclear magnetic resonance spectroscopy (NMR). The average functionality number of telechelic difunctional polymers prepared by the process of this invention is at least 1.7, as determined by nuclear magnetic resonance spectroscopy (NMR).